The invention relates generally to multi-cylinder internal combustion engines of both the two stroke and the four stroke type.
The invention also relates generally to prevention of "knocking" and to maximization of engine power.
It is known that cylinder knocking diminishes effective power output and is related to a variety of factors including the cylinder compression ratio, ignition timing or degree or amount of spark advance, the type of fuel, the cylinder operating temperature and the quantities of fuel and air present in the cylinder.
The cylinder temperature is, in part, a function of the engine cooling system, and the quantity of fuel and air present in the cylinder are determined by the air supply, fuel supply, and exhaust discharge systems.
In many prior multi-cylinder engines, the cylinders each had the same compression ratio and the particular characteristics of the cooling, air, fuel, and exhaust discharge systems caused knocking to occur at differing times for different cylinders. Engines were usually designed to avoid knocking in the most sensitive cylinder, thereby also avoiding knocking in the other cylinders.
In the past, attempts have been made to operate engines with a different spark advance for each cylinder to maximize power by avoiding knocking. However, such efforts cause difficulties in providing smooth, low speed running characteristics.